The present invention relates to a self-propelling bevel fusion-cutting machine for beveling pipes by fusion-cutter.
As for edge preparation machines of this type, the so-called rotary edge preparation machine is popular which comprises a base adapted to be fixed in position inside a pipe to be processed, a turntable mounted on said base, and a fusion-cutter such as a burner. However, such conventional edge preparation machine has the following drawbacks.
First, because of the base required besides the fusion-cutter for supporting the latter, the overall weight of the machine correspondingly increases such that machines for large pipes weigh 30 kg and those for small pipes weigh 20 kg, are inconvenient for handling. Particularly, fixedly installing the base inside a pipe takes much time and labor because of its substantial weight. Secondly, whereas pipes to be processed widely vary in diameter, in the case of the rotary edge preparation machine the limited length of the arm which supports the fusion-cutter limits the range of change of the radius of rotation of the fusion-cutter, so that covering the whole range of pipe diameters necessitates providing various sizes of edge preparation machines in accordance with pipe diameters. As a result, the economic burden increases. Thirdly, in cases where the pipe is other than round, e.g., square, the processing of the corners and straight portions requires different radii of rotation of the fusion-cutter. In this case, if the rotative speed of the turntable is constant, the peripheral speed of the fusion-cutter is high relative to the pipe corners and low relative to the straight portions, which means that the straight portions can be fusion-cut but the corners cannot. In order to avoid such situation, special measures must be taken to decrease the rotative speed of the fusion-cutter when its radius of rotation increases, thus making the machine complicated in arrangement and, moreover, adding to the weight. Fourthly, with a round pipe, if the center of rotation of the turntable is placed at the center of pipe, the direction of the flame emitted from the fusion-cutter is maintained at a constant angle with the tangential direction of the pipe periphery. With an other than round, e.g., square pipe, however, it often happens that the direction of the flame is not at a constant angle with the tangential direction of the pipe periphery. As a result, it is difficult to attain a uniform quality of fusion-cut.